Damping lowers noise levels by reducing air turbulence and mechanical vibration. If used correctly, damping is one of the most effective ways of reducing noise levels.

Using damping to reduce noise

Types of damping

Free layer (unconstrained) damping

Free layer damping is the easiest type of damping to implement. It involves glueing a viscoelastic material like a synthetic polymer to a noisy surface (eg metal) to reduce vibration and noise levels. For free layer damping to be effective, the damping material should be between one to three times the thickness of the surface being damped. This type of damping is commonly used to reduce structure borne noise (noise that occurs from an object hitting a surface, such as the floor, ceiling or wall).  Free layer damping is more effective on large thin vibrating surfaces such as metal chutes, hoppers and machine guards.

Constrained layer damping

Constrained layer damping involves sandwiching the damping material (such as a synthetic rubber) between the noisy equipment and a layer of steel or aluminium. This helps to transfer energy into the damping layer.

For damping to be effective, the structure being damped should be one third of the thickness of the viscoelastic material. If the noisy equipment or machine also vibrates use a damping material that is:

• 1.5mm if the equipment or machine being damped is between 1.5 to 3 mm thick.
• 3mm if the equipment or machine being damped is more than 3mm thick.

Constrained layer damping is commonly used to minimise unwanted vibration.

Choosing the right damping material

Talk to a competent person(external link) such as acoustic engineer to help you decide which damping material will be the most effective for your equipment or machine, and which type of damping solution you’ll need.